Annals of botany最新文献

Background and aims: In tissue culture of Juniperus chinensis, issues such as inadequate sterilization, severe browning and poor rooting have significantly hindered the widespread application of techniques of its asexual propagation. Meanwhile, J. chinensis presents three sexes: female (FP), male (MP) and monoecious (MOP), with leaf morphological differentiation into scale leaves (SL) and spiny leaves (SPL). Variations in sexes and leaf morphogenesis may affect the establishment of tissue culture systems. However, there are currently no studies that have established tissue culture systems by integrating both sex and leaf morphogenesis, and the differences in responses of explants with different sexes and leaf morphogenesis during culture remain unclear.

Methods: Using SL and SPL from FP, MP and MOP as explants, we optimized explant disinfection protocols, screening of culture medium, selection of anti-browning agents, determination of antioxidant enzyme activities, proliferation and rooting culture, plant hardening and transplantation. We comprehensively explore the differences in the process of establishing tissue culture among J. chinensis with different sexes and leaf morphogenesis.

Key results: Disinfection of explants with two types of leaf morphogenesis from three sexes can be achieved by treating them with sodium hypochlorite (NaClO) for 18 min. The basal medium suitable for the early growth of explants of the three sexes and two leaf morphogenesis types is Douglas-fir Cotyledon Revised medium (DCR). Polyvinylpyrrolidone (PVP) can inhibit browning by reducing the activity of oxidases. During the proliferation stage, explants derived from MOP demonstrate consistent hormone requirements. The efficiency of adventitious bud proliferation of SPL is notably higher than that of SL, and all proliferated adventitious buds are SPL. At the rooting stage, the rooting ability of adventitious buds from SPL is inferior to that of SL. Conversely, MOP still maintain consistent hormone demands during the rooting stage. After transplantation, sterile plants display vigorous growth, with stem segments undergoing progressive lignification, and the survival rate shows variability influenced by both sexes and leaf morphogenesis.

Conclusions: This study established a multi-dimensional tissue culture system for J. chinensis based on three sexes (FP, MP and MOP) and their corresponding SL and SPL. It analysed the differences and preferences among different sexes and leaf forms at various stages of tissue culture, providing technical support for the targeted breeding, germplasm resource innovation and industrial development of J. chinensis. Meanwhile, it offers novel perspectives for research on sex differentiation, mechanisms of leaf form transformation and other related areas in polygamous or heterophyllous tree species.

Background and aims: We aimed to elucidate how anthropogenic disturbances influence plant community assembly by integrating taxonomic, phylogenetic and functional diversity, and to quantify the relative effects of environmental drivers amid large-scale water conservancy projects.

Methods: We surveyed 123 forest community plots across the Three Gorges Reservoir Area (TGRA) in China and assessed the relative contributions of various environmental factors to plant taxonomic, phylogenetic and functional diversity by using random forest analyses and structural equation models.

Key results: We found phylogenetic overdispersion and functional clustering within plant communities in the TGRA. Anthropogenic disturbances, particularly proximity to the nearest railway line, emerged as the primary driver of the three plant diversity indicators. Notably, none of the functional traits displayed significant phylogenetic signal, indicating a decoupling of functional and phylogenetic diversity occurred in areas of high human disturbances. As the intensity of disturbances increased, phylogenetic diversity increased, with plant communities shifting from clusters of closely related species towards more random assemblages. In contrast, functional diversity decreased, with communities becoming more functionally similar. This suggests that functional traits may evolve independently of phylogenetic history, challenging traditional perspectives on community assembly.

Conclusions: Our study demonstrates a critical divergence in biodiversity responses to anthropogenic pressure: while disturbances enhance phylogenetic diversity through environmental filtering, they simultaneously induce functional homogenization via trait-mediated selection processes. This divergence highlights the inadequacy of single-metric assessments and underscores the importance of integrative frameworks for understanding community assembly in human-modified ecosystems.

Background and aims: Phosphorus (P) allocation as dependent on a plant's age is a critical yet understudied factor in the adaptive strategies of shade-tolerant plants. We investigated how Coptis chinensis, a perennial medicinal plant species, allocates leaf P fractions and exhibits leaf structural modifications in response to the understorey light environment.

Methods: By analysing leaf P fractions, chlorophyll concentrations, photosynthetic parameters and leaf anatomical traits in juvenile (2- and 3-year-old) and adult (5-year-old) plants, we uncovered age-dependent shifts in leaf P fractions that balanced photoprotection and growth.

Key results: Leaves of juvenile plants allocated a greater proportion of P to nucleic acid P (PN), exhibited higher photoprotective pigment-to-chlorophyll ratios and maintained greater specific leaf area (SLA) with thinner tissue structures. The proportion of PN was positively correlated with photoprotective pigment-to-chlorophyll ratio, indicating that enhanced PN allocation contributes to light-stress resilience and early-stage growth. In contrast, as plants progressed to the adult stage leaves showed a marked shift towards higher allocation to metabolite P (PM), which correlated with higher photosynthetic rates, higher chlorophyll concentrations and increased Rubisco enzyme activity. Concurrent structural modifications, including thicker palisade mesophyll and reduced SLA, further supported enhanced photosynthetic performance. This developmental transition from PN-dominant to PM-dominant allocation thus reflects a physiological acclimation that sustains photosynthesis and improves photosynthetic P-use efficiency under shaded conditions.

Conclusions: Our findings highlight a dynamic interplay between P allocation and structural acclimations in C. chinensis leaves, revealing an adaptive strategy that balances photoprotection and growth across different ages. By demonstrating how resource allocation shifts with age in a shade-adapted perennial, this study offers novel insights into the evolutionary strategies that underpin long-term survival and productivity in understorey environments.

Background and aims: The limited understanding of how early life-history transitions respond to changing environmental conditions constrains our knowledge of climate change impacts. Soil salinity intensification is a significant global issue, yet the eco-evolutionary aspects of germination responses to salinity gradients remain understudied.

Methods: We employed phylogenetic comparative methods, utilizing a century of published records and data on germination responses to salinity gradient, ecological niches and seed traits, to test hypotheses on the variation and evolution of germination tolerance to salinity across 327 plant species. We related germination salinity tolerance to growth forms, lifespans and biomes to examine potential eco-evolutionary factors underlying germination responses to a salinity gradient.

Key results: Our results reveal significant variation in germination salinity tolerance among different growth forms, lifespans and biomes. Germination salinity tolerance parameters are evolutionarily labile and environmental conditions predominantly drive germination tolerance to salinity gradients by stabilizing selection. Ecological niche and seed traits, such as seed mass and embryo length, significantly mediate germination responses to salinity.

Conclusions: This first quantitative assessment of the evolutionary tempo and mode of germination salinity tolerance across diverse plant taxa provides novel insights into how evolutionary processes shape stress tolerance during germination, emphasizing the role of seed mass and growth forms in driving salinity tolerance to germination. These findings enhance our understanding of the strategies plants employ to navigate salinity stress.

Background and aims: Fasciclin-like arabinogalactan proteins (FLAs) function in diverse plant physiological processes, particularly cell wall biosynthesis and tension wood (TW) formation. This study aimed to identify Betula platyphylla FLA genes associated with secondary xylem and TW development, thereby elucidating molecular mechanisms underlying xylogenesis to facilitate molecular improvement strategies.

Methods: Tissue-specific expression of two FLA genes (BpFLA1, BPFLA2) was analysed via quantitative real-time PCR. BpFLA1/2-overexpressing transgenic lines and bpfla1 knockout mutants were generated using the pROK II vector and CRISPR-Cas9 technology. Anatomical phenotypes, cell wall composition and TW development were subsequently investigated.

Key results: Two FLA genes (BpFLA1, BpFLA2) were identified in the birch TW transcriptome. Phylogenetically, BpFLA1 and BpFLA2 exhibit conserved evolutionary relationships and structural domains. Both genes were highly expressed in mature stems but suppressed by mechanical stimuli. BpFLA1/2-overexpressing transgenics displayed slightly suppressed growth, reduced cell wall thickness, enlarged xylem vessel area and notably inhibited TW formation following artificial bending. Conversely, bpfla1 knockout mutants exhibited significant thickening of xylem fibre cell walls, a phenotype contrasting sharply with OE lines.

Conclusion: BpFLA1/2 functions as a critical regulator of cell wall development and a negative regulator of xylem fibre and TW formation in birch. Therefore, this study identifies BpFLA1/2 as a novel target for genetic improvement. BpFLA1/2 overexpression potentially enhances wood straightness and quality, whereas its suppression or knockout may benefit cellulose production for pulpwood applications.

Background: Foliar water uptake (FWU) and its role in hydraulic redistribution are critical yet understudied mechanisms, particularly in temperate tree species of Europe.

Methods: This study investigates FWU in beech (Fagus sylvatica L.), with a focus on its contribution to the tree's water balance beyond leaf level. By using a combination of different imaging techniques such as silver nitrate tracing, positron emission tomography (PET) and autoradiography, we identified foliar water uptake from the point of entry to its subsequent transport.

Key results: The ionic tracer, silver nitrate (AgNO3), precipitated mainly at trichome bases and extended into subepidermal tissues, enabling the identification of water entry points. However, its inability to reach deeper vascular structures limited the ability to draw conclusions about further water transport and redistribution. Therefore, PET imaging and autoradiography were used and successfully visualized reverse sap flow of radiotracer-labelled water from treated leaves to connected branches, driven by a significant water potential gradient Δψ of 1.4 ± 0.9 MPa. Compartmental modelling quantified a net exchange rate eX-P of 0.15 ± 0.07 min-1 between xylem and surrounding parenchyma and a front velocity vFWU of 3.31 ± 0.56 mm min-1 under the imposed Δψ.

Conclusions: These findings demonstrate that FWU may actively contribute to replenishing branch water pools, emphasizing its role as a critical hydraulic mechanism. This research underscores the utility of integrating PET imaging with complementary methods to better understand FWU dynamics and its implications for plant water budgets under changing climatic conditions.

Background and aims: Flower petal integrity affects the success of plant reproduction and ecological adaptability. The mechanical resistance of plant organs indicates their capacity to withstand physical damage and preserve structural integrity. However, little is known about the mechanical resistance of flowers and their differences from leaves.

Methods: To address the aforementioned research gaps, we quantified flower petals from 43 species and leaves from 86 species, employing two forces that characterize mechanical resistance: force to punch and force to tear. For force to punch, three different diameter punch needles were used to measure and three methods were employed for calibration. Additionally, we measured functional traits of petals and leaves.

Key results: We found that petals have significantly lower mechanical strength than leaves in both punch and tear forces. The force to punch and force to tear of petals and leaves were positively correlated with tissue thickness, cuticle thickness and dry mass per unit area. The vein density of petals was positively correlated with force to punch and force to tear, while force to tear was negatively correlated with floral tissue density after phylogenetic independent contrast correlation analysis. For reticular venation leaf, the vein density had no significant relationship with force to tear, but was positively correlated with tissue density.

Conclusions: Our results indicated that there were differences in the structural basis of mechanical resistance between flowers and leaves. Regarding the most classical mechanical testing method, force to punch, different needle diameters and calibration methods can affect the results for both the petal and leaf. Our research results provide an important reference for better understanding the ecological adaptability of flowers.